1. Field of the Invention
The invention relates to a suction electrocoagulator apparatus having an anti-clogging tip which includes a thermally insulating sleeve that extends from the distal end of the hollow, conductive cannula tube into the interior cavity of said tube.
2. Description of Related Art
The coagulation of bleeding blood vessels using electrically conductive suction tubes, also referred to as cannulas, is a technique widely used for over two decades. A combined electrocautery and suction tube instrument is typically employed in surgery wherever excessive blood must be removed from the bleeding site in order to facilitate hemostat of bleeding vessels using the electrocautery feature of the instrument.
Commercially available suction coagulators made expressly for electrocautery hemostat procedures generally have the following common components:
(A) A hollow, metallic, conductive cannula tube having a suitable thickness of non-conducting electrical insulation on its exterior. The electrical insulation is absent from the first few millimeters on the tube's distal end in order to form an annular ring for electrocautery procedures. The sole purpose of the insulation is to protect the patient and doctor from cautery burns that would result from contact with the outside of the metallic tube when it is energized.
(B) A non-metallic or electrically insulated handle. The handle includes a suction cavity or passageway running through its length that terminates in a suction fitting at one end for connection to a suction source. At its proximal end the handle is hermetically coupled to the hollow, metallic tube so that the suction cavity of the handle communicates directly with the suction channel of the tube. The handle may also have a venting passageway that connects the main suction cavity with a vent hole on the handle's exterior. The surgeon uses finger pressure on the vent hole to control the amount of suction applied.
(C) A power cord, typically in an insulated wire, is used to connect the suction coagulator to a high frequency current generator. The power cord enters the handle and is electrically connected to the proximal end of the conductive suction tube using various known connecting techniques.
One of the major problems with electrocautery suction devices is that the tips tend to clog with burned tissue and coagulated blood. In theory, the suction is supposed to remove the clog but the suction itself produces some problems.
One approach has been to control the flow of air through the suction tip by means of a vent hole that can be manipulated by the surgeon. A useful description of the prior art problems is found in my prior U.S. Pat. No. 4,932,952 entitled ANTISHOCK, ANTICLOG SUCTION COAGULATOR. The following patents were cited as being relevant to that approach: U.S. Pat. Nos. 2,888,928; 3,595,234; 3,610,242; 3,828,780; 3,857,945; 3,974,833; 4,427,006; 4,562,838; and 4,719,914.
Another approach to minimize the coagulating of tissue in an electrocautery suction instrument is described in U.S. Pat. No. 3,902,494 entitled SUCTION SURGICAL INSTRUMENT. The general concept described therein provides for an electrode at the tip of the instrument located in such a way as to impede the introduction of tissue mass into the tube. By restricting the size of the opening with the conducting electrode, it is possible to filter out tissue that otherwise might clog the instrument downstream. One embodiment described in the text of U.S. Pat. No. 3,902,494, but not illustrated in its drawings, comprehends an electrical lead shaped as a tube which encompasses the suction shaft 10. The purpose appears to be to increase the stiffness of the suction shaft. In that embodiment, it is assumed that the electrode tip of the suction device is likewise restricted to prevent tissue clogging as taught by the other illustrated embodiments of the invention. Insofar as understood, U.S. Pat. No. 3,902,494 is directed at the concept of preventing tissue clogging and does not appear to address the more difficult issue of clogging caused by the coagulation of blood at the mouth of the cannula due to the heat generated by the electrocautery effect.
U.S. Pat. No. 4,682,596 entitled MEDICAL HIGH FREQUENCY COAGULATION INSTRUMENT describes a specialized structure incorporating an insulating hose inside of a ring electrode which is part of a much more complicated overall structure involving a second ring electrode and an exterior insulating layer as well as an intermediate insulating layer. The purpose of the device appears to provide a supply of "flushing liquid" which emerges around the interior electrode and then is sucked down through the central shaft of the interior electrode.
U.S. Pat. No. 4,682,596 and its counterpart U.S. Pat. No. Re. 22,925 both describe a catheter employing an electrode and an electrically insulating tube. In that embodiment, the electrode appears to cover the entire front face of the device as illustrated in FIGS. 3 and 4 thereof. There is a discussion in column 8, lines 44-47 that addresses the insulating properties of the support for the electrode tip.
Lastly, U.S. Pat. No. 4,347,842 entitled DISPOSABLE ELECTRICAL SURGICAL SUCTION TUBE AND INSTRUMENT is cited as being of general possible relevance only.
While the prior art selectively discloses the concept of restricting tissue from entering the tip of an electrocautery tube so as to prevent clogging of the tube, nevertheless, it does not appear to appreciate the problem of blood coagulation at the tip due to electrocautery heating. Accordingly, none of the prior art located and described above appears to fully appreciate the necessity of providing appropriate thermal insulation at the tip in order to avoid blood coagulation. The invention described in detail later in this specification, provides a dramatic improvement over prior art devices such as described above by virtue of the fact that it substantially eliminates the problem previously associated with the formation of eschar, i.e. blood char, in the tip of electrocautery suction devices.